Use a proper table for module TOC

[nyalldawson]

And include the brief description of classes in the table.

Before:

After:

[nyalldawson]

Now groups classes by logical group, eg:

[nyalldawson]

@3nids what's involved in publishing a new version to the actual site? When's that triggered?

[3nids]

Every push to main on this repo will publish a new version, otherwise it's at least once per week if there is no activity here.

It used the Deb packages, so any change on QGIS source takes a couple of days to be reflected.